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Sunday, April 10, 2011

Why are squirrels so stupid?

I imagine I’ve heard this question one hundred times if I’ve heard it once.

Perhaps this situation is familiar to you: sitting alongside the road, a squirrel’s big black eyes go wide as a car barrels down upon it. Suddenly, seemingly just moments before the vehicle passes the small mammal, it darts into the road. Knuckles clench the wheel and feet slam on the brakes as the imminent disaster approaches. So close that the squirrel’s tail likely brushes the rubber of the front tire, the animal reaches the other lane and apparent safety. All in the car exhale deeply as the crisis is averted.

Then, as relieved smiles are exchanged all around, the squirrel leaps into motion again. To everyone’s shock and horror, the squirrel doubles back to head back across the road. This time, the outcome isn’t as happy.

The driver winces, maybe slaps the dashboard, and exclaims, “It ran right under the tire! There was nothing I can do. Why are squirrels so stupid!?”

Given the squirrel’s seemingly suicidal behavior, it’s a fair question to ask. But, what’s the answer? How did the squirrel survive as a species if they’re always jumping in front of cars?

I imagine that thousands of years ago, before we had roads, let alone cars barreling along them, the one thing a squirrel had to worry about, the one thought that pre-occupied their little squirrel brains more than anything else, was of being eaten by another animal. And what type of animal were they most worried about? I would venture a guess and say birds of prey, like hawks.

Hawks are efficient predators. One of their most effective hunting strategies involves sitting high in a tree overlooking an open area, like a field. Driving along the interstate, you may have noticed the occasional red-tailed hawk sitting on a powerline or exposed branch, intently peering down into the grassy road shoulder. They’re waiting and looking for their next meal. When a snake, small bird, or mammal ventures into this area, the sharp-eyed hawk flies into motion and quickly swoops down onto their hapless prey.

Imagine you’re a football player and you’re running full speed at someone else holding the ball, intent on tackling them as quickly as possible. If the person with a ball is standing still, your job is easy. But what if they suddenly shift ten feet to the left? You’ve got to quickly compensate, which slows you down as you recalibrate onto your target. Then, as soon as you’ve got a bead on them again, they shift to the right, heading back to where they came from. Your hips swivel in response to their movement, slowing you down some more and throwing you off balance.

Squirrels use the same principle to avoid hawks and other birds of prey. If a squirrel notices a hawk swooping down, they’re going to try to zig and zag so the hawk has trouble zeroing in. If they do it right, the hawk is likely to miss the squirrel altogether and crash into the ground. In the meantime, the squirrel makes their escape into the dense brush or branches of a nearby tree.

When a squirrel notices a truck barreling down the road, it doesn’t have time to figure out the make and model, it perceives a threat and it reacts. And its reaction is based on what’s helped them thwart their primary threat for thousands of years. It’s not that squirrels are stupid; it is just that the behavior that’s worked for them for so long isn’t much help in avoiding new threats. Given enough time, we may find that some day in the future squirrels are beginning to run in straight lines. This may help them avoid cars, but it will also help hungry hawks. In any case, if this change in behavior is possible, it hasn’t happened yet. In the meantime, and if you’re interested in avoiding flattened squirrels, just slow down. It gives the squirrel more time to react and you’re less likely to have to swerve to miss them.